It is common practice to process contaminated gases, such as contaminated ambient air or exhaust or flue gases, by passing the gases through a scrubbing tower. Conventional scrubbing towers usually contain water or other chemically reactive solutions that react with or absorb the undesirable elements in a gas stream passed through the scrubbing tower. For example, the removal of oxides of sulfur, during the burning of coal in utility plants and the like, is normally accomplished by utilizing chemical solutions containing alkaline compounds that react with the oxides of sulfur to form soluble sulfites and sulfates.
Relatively complex baffle systems within the scrubbing zone of the tower promote liquid-gas contact. Alternatively, contact elements in the form of stationery or floating beds have been used whereby the cleaning solution coats the elements and, as the gas passes through the beds, the oxides of sulfur will contact the scrubbing solution on the contact elements. Apparatus and methods of the above types require high levels of energy and are often-times cost prohibitive.
Air pollution control systems are also required for all contemporary refuse-to energy plants for the purpose of cleaning flue gases. Present day environmental regulations require scrubbers and electrostatic precipitators or baghouses. These systems are quite effective in the reduction of acid-gas emissions and particulate levels. The most common scrubber used is the so-called dry scrubber which can be operated with relatively low power requirements.
The dry scrubber, so-called because of its dry reaction product, involves the spraying of a lime slurry into a flue gas stream. Residence time is sufficient for mixing and neutralizing to occur. Contact between the finely dispersed droplets and the flue gas will cause the water to evaporate rapidly. Relatively high acid-gas removal efficiency is achieved and a dry reaction product is obtained. Systems of this type require close attention to the temperature of the entering flue gases which must be maintained sufficiently high to completely evaporate the slurry water. Further, the design of the boiler and heat recovering equipment must be compatible with scrubber requirements at all operating loads.
A typical scrubber-washer system presently used for industrial applications is the so-called Fumatrol system, manufactured by the Pollution Control Division of Savko Plastics of Santa Clara, Calif. The system can be tailored for the treatment of exhaust gases that contain large amounts of H.sub.2 or NO.sub.2 and exhaust gases of general industrial character (e.g., wet stations). These scrubbing systems find particular application with epitaxial silicone chemical vapor deposition (CVD) reactors, silicone etch and polish stations, associated cleaning operations, precious metal reclaiming, printed circuit board operations, refining operations and wet stations, i.e., wafer fabrication.
This type of scrubber system includes multiple stages wherein the contaminated gases are subjected to intense scrubbing and washing to achieve the desired gas-to-liquid contact. The gases flow downwardly through a plurality of tubes in each stage during which time they are subjected to a fine mist spray to prevent the retention of solid formation on the inner surfaces of the tubes. The gases exit the tubes and pass through a water bath to expose a relatively large gas-plane for water molecules of the bath to contact. The gases then move upwardly for processing through the next adjacent stage
The air pollution problem existing in commercial establishments, such a beauty parlors and restaurants, is normally confronted with the use of standard dry filters mounted in air conditioning systems and the like. Beauty parlors, for example, tend to exude various noxious elements, such as acetates, peroxides and sulfides. Dry filters are unable to clean the polluted air to render it non-toxic, odorless and substantially clean.
U.S. Pat. Nos. 3,954,921; 4,156,712; 4,164,399; and 4,818,259 also disclose various conventional scrubber-type systems, adapted for industrial uses of the type described above.